Pilot operated automatic expansion valve

ABSTRACT

In the preferred form, a vertical receiver housing incorporates a receiver entrance and an outlet fitting at the top and an inlet fitting at the bottom of a vertical evaporator. A coaxial tube extends from the outlet fitting down through the receiver to a pilot control enclosure containing an evacuated pressure responsive bellows provided with a coaxial follower for operating the pilot valve in accordance with the outlet pressures. The pilot valve controls the flow of high-pressure liquid from the receiver to the pistonhead of the piston slotted sleeve valve which forms the main valve to control the flow of liquid refrigerant from the receiver into the bottom inlet fitting of the evaporator. This pilot control arrangement controls the outlet pressure within a very small differential between idling and maximum speed of the compressor.

United States Patent 3.220311 ll/l965 NOrdquest.

62/222X 3,320,763 5/1967 Harnish 62/204X 3,402,566 9/1968 Leimbach. 62/225X ABSTRACT: In the preferred form, a vertical receiver housing incorporates a receiver entrance and an outlet fitting at the top and an inlet fitting at the bottom of a vertical evaporator. A coaxial tube extends from the outlet fitting down through the receiver to a pilot control enclosure containing an evacuated pressure responsive bellows provided with a coaxial follower for operating the pilot valve in accordance with the outlet pressures. The pilot valve controls the flow of high-pressure liquid from the receiver to the pistonhead of the piston slotted sleeve valve which fonns the main valve to control the flow of liquid refrigerant from the receiver into the bottom inlet fitting of the evaporator. This pilot control arrangement controls the outlet pressure within a very small differential between idling and maximum speed of the compressor.

PILOT OPERATED AUTOMATIC EXPANSION VALVE This invention pertains to a receiver, expansion valve and evaporator arrangement particularly useful in automobile air conditioners.

When the refrigerant compressor is driven directly by an automotive engine as in most auto air conditioners, there is such a great tendency for the evaporators to frost and freeze up under cool outdoor temperatures and high engine speeds that it has been customary to provide pressure-regulating valves in series with the suction lines to prevent the evaporator temperature from falling below water-freezing temperatures. Such valves are expensive and their throttling action reduces the thermal efficiency of the system so that more power is required to produce the refrigeration desired for air-conditioning.

It is an object of this invention to provide a liquid refrigerant control arrangement for controlling the flow of liquid refrigerant into the evaporator in such a way that the pressure within the evaporator is maintained at such a substantially constant level regardless of compressor speeds that the temperature of the evaporator is maintained a few degrees above water-freezing temperature.

It is another object of this invention to provide an automatic expansion valve responsive to evaporator pressures which will supply sufficient liquid refrigerant to the evaporator to prevent the evaporator temperature from falling below waterfreezing temperatures even though the compressor is withdrawing evaporated refrigerant at a high rate.

it is another object of this invention to provide an expansion valve in which the outlet pressure is reduced at a predetermined low rate as the inlet pressure increases at a high rate.

it is another object of this invention to provide an expansion valve in which a pilot valve responsive solely to the pressure of the refrigerant in the evaporator controls the position of a large main valve capable of large volumes of refrigerant flow with a minimum of restriction.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein preferred embodiments of the present invention are clearly shown.

IN THE DRAWINGS FIG. 1 is a diagrammatic view of an automobile air-conditioning refrigerating system embodying one form of my invention;

FIG. 2 is a fragmentary vertical sectional view in two parts through the combined receiver and automatic expansion valve as shown in FIG. 1.

Referring now to FIG. 1, there is illustrated an automobile refrigerant compressor provided with a belt pulley 22 adapted to be driven at a fixed speed ratio to engine speeds by a belt from a pulley on the front of the automobile engine crankshaft. This compressor 20 withdraws evaporated refrigerant from the suction conduit 24 and pumps the compressed refrigerant through the discharge conduit 26 into the air-cooled condenser 28 normally located in front of the automobile radiator.

The compressed refrigerant is cooled and liquefied in the condenser and flows therefrom through the conduit 30 to a fitting 32 through which it discharges into the top of a tubular vertical receiver housing 34. In the bottom of the receiver housing 34 is an automatic expansion valve housing 36 which may be of cast aluminum. it is supported by having its reduced lower end fitting an annular shoulder in the large nipple 38 in the bottom of the receiver housing 34. This nipple 38 is provided with a double flange 40 which extends outwardly between the horizontal flange 42 at the bottom of the housing 34 and the horizontal flange 44 of the cup portion 46 provided at one side with an opening 48 which connects directly with an inlet fitting 50 connecting, in turn, with the inlet 52 at the bottom of the vertical multiple pass refrigerant evaporator 54.

The top of the evaporator 54 is provided with an outlet connection 56 connecting with the outlet fittings 57, 58 and 60 which are welded or otherwise bonded together to form an outlet passage 62 connecting with the suction conduit 24. The fitting 58 has an outwardly extending horizontal flange 64 which is bolted to a horizontal plate 66 and the horizontal upper flange 68 of the receiver housing 34. The outlet fitting 58 is. provided with a removable gage connection and valve 70 which is sealed thereto by a gasket 72 so that it can be removed for access to the coaxial tube 74. This coaxial lowpressure gas conducting tube 74 has its upper end extending through the horizontal dividing plate 66 with a sealing gasket 76 surrounding the tube within the plate 66 to prevent leakage of refrigerant from the receiver housing into the outlet passage 62. The plate 66 as well as the fittings are provided with suitable O-ring-type gasket seals to prevent leakage. The space between the tube 74 and the receiver housing'34 below the plate 66 may be provided with a bag 84 of dessicant material for keeping dry the refrigerant.

The gas tube 74 extends down to a removable flanged fitting closing and sealing the top of the expansion valve housing 36 and is sealed thereto by a gasket 78 to prevent leakage.

The expansion valve housing 36 is provided with a threaded passage 80 coaxial with the gas tube 74 which is provided with a hollow threaded adjusting bushing 82. The bottom of the hollow bushing 82 is fastened to the hollow coaxial upwardly extending projection upon the upper base 86 of a sealed evacuated bellows 88 containing a compression-type coil spring 90. The upper base 86 is provided with a sealed charging tube 92 extending up into the bushing 82. The bottom of the bellows 88 is closed and contains a bottom spring retainer 94. The upper base 86 is provided with an integral spring retainer for supporting the upper end of the enclosed compression spring which expands the bellows 88. The sealed bellows 88 is located within an enlarged chamber 96 coaxial with the valve body 36 and the tube 74. A second spring 98 surrounds the adjusting bushing 82 and extends from the shoulder within the housing 36 surrounding the threaded bushing 82 down to the upper face of the upper base 86 of the bellows 88 which presses downwardly to prevent any looseness and to apply a frictional force to prevent undesired rotation of the parts. By this arrangement the gage connection 70 can be removed and a long tool with a hexagonal end can be extended through the top opening provided by the removal of the gage connection 70 down through the tube 74 to fit the hexagonal aperture in the bushing 82 which then can be rotated to set the location of the sealed bellows 88. This will adjust the pressure to be maintained in the evaporator 54.

The bottom of the bellows 88 rests upon a cylindrical follower 121 which projects downwardly within a bore in the valve bushing to engage the adjacent end of and oppose the square shaped needle valve 123 which also is slidably mounted in the valve bushing 125 in the bottom of the bellows chamber 96. The needle valve 123 contains a bottom cavity receiving a small compression type coil spring 127 which urges the conical point into the small orifice 157. The bottom of this spring 127 is retained by the perforated cup-shaped member 129 held in one end of the liquid refrigerant passage 131. The bottom of the housing 36 is surrounded by a cylindrical filter 133 which is supported laterally by the encircling coil spring 134 which permits the liquid refrigerant in the receiver housing 34 to flow into the passage 131 leading to the needle valve 123 in the housing 36 and also allows liquid refrigerant to flow into the diametrically opposite horizontal slots 135 leading to the piston sleeve valve 143 in the bottom of the housing 36. The pilot valve bushing 125 has a side outlet 159 connecting with passages 137 and 139, in turn connecting with an annular passage 141 surrounding the pistonhead of the pistonsleeve valve 143. The piston sleeve valve 143 is hollow and contains a compression-type coil spring 145 extending from the head down to the perforated spring support 147 above the inturned flange 149 surrounding the opening 151 at the bottom of the double flanged member 38 which communicates with the inlet passage 48 for flow into the bottom of the evaporator. The valve housing 36 is provided with a groove at the bottom containing a seal ring 150 engaging the double flanged nipple member 33. The piston sleeve valve 143 is provided with diametrically opposite upper and lower slots 153 and 155. The upper slots 153 provide a controlled leakage from the passage 1411 to allow the spring 145 to force upwardly the piston sleeve valve 143. The lower slots 155 are adapted to register with the slots 135 for full flow of refrigerant.

OPERATION When the pressure in the evaporator 54 rises its pressure rise will be communicated through the outlet passage 62, the gas tube 74, the housing 75 and the bushing 82, which has a small hole 157 in its side for flow to the bellows chamber 96 where the bellows will be slightly compressed to allow an upward movement of the follower 121 and the pilot valve 123. The collapsing pressure upon the bellows 88 will cause the bottom wall of the bellows and the follower 121 to move upwardly to free the needle valve 123 for upward closing movement to place its point in the orifice 157 to prevent flow from the passage 131 to the passage 141. The upward force of the spring will push upward the piston sleeve valve 143. Any liquid or gas trapped above the pistonhead will leak through the clearance between the surrounding cylindrical surfaces to the upper slot 153.

Should the pressure in the outlet passage 62 fall, there will be a sizable but relatively small movement of gas out of the bellows chamber 96 through the hole in the side of the threaded bushing 32 and up the gas tube 74 to the outlet passage 62 to equalize the pressures. This will reduce the pressure in the chamber 96 surrounding the bellows 88 thereby allowing a small expansion to push downwardly the follower 121 and the needle valve 123 against the force of the spring 127. This permits a small flow of liquid refrigerant through the cylindrical filter 133, the passage 131, around the needle 123 through the small orifice 157 and the passage 159 into the chamber 137 from which it flows through the passage 139 into the annular passage Mil surrounding the pistonhead of the piston sleeve valve 143. This forces the piston sleeve valve 143 to move downwardly until the slot 155 begins to register with the slot 135. This causes additional flow of liquid refrigerant through the cylindrical filter 133, the aligned slots 135 and 155 into the interior cavity of piston sleeve valve 143. The refrigerant then flows downwardly through the center bore and the bore in the housing 36 containing the piston sleeve valve 143, through the opening 151, the chamber 46 and the opening 48 into the bottom of the evaporator 54.

The increased flow of liquid refrigerant into the evaporator 54 provides more liquid refrigerant and evaporation of the refrigerant which will raise the pressure within the outlet passage 62 and the bellows chamber 96 to cause the bellows 38 to contract and move upwardly the follower 131 and the needle valve 123 to decrease the opening of this pilot valve 123. The bellows 88, since it is evacuated, is completely responsive to the pressure in the chamber 96 surrounding it which is substantially equal to the pressure in the outlet fitting 62. This will reduce the supply of refrigerant to the pistonhead so that leakage past it into the upper slot 153 permits the piston sleeve valve 143 to move upward slightly to introduce a greater throttling action upon the flow through the slots 135 and 155.

It should be noted that when closed, the needle valve 123 has a pressure on the bottom surface which corresponds to the pressure within the condenser 23. This will tend to lower the outlet pressure of the evaporator 56 about 1 lb. for every 50 lbs. rise in the receiver and condenser pressure. This proportion is inverse to the efiective area of the bellows 83 compared to the area of the orifice 157. This is advantageous since the rise in condenser and receiver pressure will be substantially in proportion to the rise in the outdoor or ambient temperature.

When there is a rise in the outdoor ambient temperature it is possible to operate the evaporator at a lower temperature without freezing to satisfy the demand for more refrigeration at higher ambient temperatures. Therefore, this small closing pressure on the needle valve 123 improves the efficiency of the expansion valve and capacity of the refrigerating system. With this arrangement there is much less likelihood of freezing the evaporator and yet the system is very efficient since there is no throttling required at the evaporator outlet and the evaporator is kept near water-freezing temperatures when the ambient temperatures are high.

The receiver housing 34 is provided on the side with a gage connection and a sight glass 167. The housing 34 may be flattened on one side to facilitate welding of the fitting 32 and the gage connection 165 and the sight glass to the walls thereof. When the gage connection 70 is removed a sufficiently long simple hexagonal rod or a sufficiently long Allen type wrench or any other sufficiently long rod provided with an end adapted to fit the entrance of the bushing 32 may be used as a tool for turning the bushing 32. Such a tool should be sufficiently long to extend from the bushing 32 up through the gas tube 74 and the outlet fitting 58 and extend above sufficiently far for manipulation. The upper end portion of such a tool outside the fitting 58 may be bent laterally or otherwise formed to provide a handle or other means of turning it upon its axis.

While the embodiments of the invention as herein disclosed constitute preferred forms, it is to be understood that other forms might be adopted.

1 claim:

1. A low-differential high-capacity expansion valve for controlling the flow of refrigerant from the high-pressure portions to the low-pressure portions of refrigerating systems for maintaining a substantially constant low-pressure in the low-pressure portions including a housing having an inlet adapted to be connected to said high-pressure portions, and an outlet adapted to be connected to said low-pressure portions, wherein the improvement comprises an evacuated enclosure provided with a flexible diaphragm means, said housing being provided with a chamber connected to said low-pressure portions containing said evacuated enclosure and diaphragm means, said housing being provided with a piston chamber containing a slidable piston valve having a high maximum rate of flow connected between said inlet and said outlet and provided with a piston extending into said piston chamber, said housing having a passage extending from the said high-pres sure portions to said piston chamber, and a pilot valve connected in series with said passage and operably connected to said flexible diaphragm means for controlling the flow to said piston to select the position of said piston valve in accordance with the pressure of said low-pressure portion.

2. Refrigerating apparatus including evaporating means having an inlet and an outlet, a tubular housing connected to said inlet and said outlet and extending from said outlet to said inlet, said housing having an outlet passage for evaporated refrigerant connected to said outlet and having an entrance for liquid refrigerant adjacent to but separated from said outlet passage and an inlet passage extending from said entrance to said inlet of said evaporating means, said housing being provided with a valve housing adjacent said inlet containing an enclosure and a piston chamber, said enclosure containing an evacuated sealed casing comprising a flexible diaphragm means, a piston valve in said piston chamber containing valve slots, said valve housing having valve slots in the walls of said piston chamber with which the valve slots in the piston are adapted to align in predetermined positions of the piston for maximum flow of refrigerant from said inlet passage to said inlet, said valve housing having pilot valve passage means extending from said inlet passage to said piston chamber, pilot valve means in said pilot valve passage, said flexible diaphragm means having operating means for operating said pilot valve in accordance with the pressure in said enclosure in the valve housing, and means forming a control passage extending from said outlet passage through said housing to said enclosure for operating said flexible diaphragm means in response to the pressure conditions in said outlet passage for controlling the position of said piston valve and the registering of its slots with the slots in the valve housing.

3. Refrigerating apparatus as defined in claim 2 in which said housing is provided with an access opening and a removable closure for said access opening which are coaxially aligned with the evacuated sealed casing and said flexible diaphragm means and said control passage, said valve housing being provided with adjusting means in alignment with said control passage for adjusting the location of said evacuated sealed casing, said control passage and said access opening being large enough to receive a tool for operating said adjusting means.

4. Refrigerating apparatus as defined in claim 2 in which filtering material surrounds the valve housing adjacent the valve slots therein.

5. A low-differential high-capacity expansion valve for controlling the flow of refrigerant from the high-pressure portions to the low-pressure portions of refrigerating systems for maintaining a substantially constant low-pressure in the low-pressure portions including a housing having an inlet adapted to be connected to said high-pressure portions and an outlet adapted to be connected to said low-pressure portions, means forming within said housing a diaphragm chamber provided with diaphragm means adapted to be exposed to the pressure within said low-pressure portions, a main valve of large maximum flow capacity located between said inlet and said outlet in said housing, a fluid motor for operating and selecting the position of said main valve to control the flow from said inlet to said outlet, said housing having passage means extending from said inlet to said fluid motor, and a pilot valve operated by said diaphragm means located in series with said passage means for controlling the flow to said fluid motor to select the position of said main valve in accordance with the pressure of said low-pressure portions. 

1. A low-differential high-capacity expansion valve for controlling the flow of refrigerant from the high-pressure portions to the low-pressure portions of refrigerating systems for maintaining a substantially constant low-pressure in the lowpressure portions including a housing having an inlet adapted to be connected to said high-pressure portions, and an outlet adapted to be connected to said low-pressure portions, wherein the improvement comprises an evacuated enclosure provided with a flexible diaphragm means, said housing being provided with a chamber connected to said low-pressure portions coNtaining said evacuated enclosure and diaphragm means, said housing being provided with a piston chamber containing a slidable piston valve having a high maximum rate of flow connected between said inlet and said outlet and provided with a piston extending into said piston chamber, said housing having a passage extending from the said high-pressure portions to said piston chamber, and a pilot valve connected in series with said passage and operably connected to said flexible diaphragm means for controlling the flow to said piston to select the position of said piston valve in accordance with the pressure of said low-pressure portion.
 2. Refrigerating apparatus including evaporating means having an inlet and an outlet, a tubular housing connected to said inlet and said outlet and extending from said outlet to said inlet, said housing having an outlet passage for evaporated refrigerant connected to said outlet and having an entrance for liquid refrigerant adjacent to but separated from said outlet passage and an inlet passage extending from said entrance to said inlet of said evaporating means, said housing being provided with a valve housing adjacent said inlet containing an enclosure and a piston chamber, said enclosure containing an evacuated sealed casing comprising a flexible diaphragm means, a piston valve in said piston chamber containing valve slots, said valve housing having valve slots in the walls of said piston chamber with which the valve slots in the piston are adapted to align in predetermined positions of the piston for maximum flow of refrigerant from said inlet passage to said inlet, said valve housing having pilot valve passage means extending from said inlet passage to said piston chamber, pilot valve means in said pilot valve passage, said flexible diaphragm means having operating means for operating said pilot valve in accordance with the pressure in said enclosure in the valve housing, and means forming a control passage extending from said outlet passage through said housing to said enclosure for operating said flexible diaphragm means in response to the pressure conditions in said outlet passage for controlling the position of said piston valve and the registering of its slots with the slots in the valve housing.
 3. Refrigerating apparatus as defined in claim 2 in which said housing is provided with an access opening and a removable closure for said access opening which are coaxially aligned with the evacuated sealed casing and said flexible diaphragm means and said control passage, said valve housing being provided with adjusting means in alignment with said control passage for adjusting the location of said evacuated sealed casing, said control passage and said access opening being large enough to receive a tool for operating said adjusting means.
 4. Refrigerating apparatus as defined in claim 2 in which filtering material surrounds the valve housing adjacent the valve slots therein.
 5. A low-differential high-capacity expansion valve for controlling the flow of refrigerant from the high-pressure portions to the low-pressure portions of refrigerating systems for maintaining a substantially constant low-pressure in the low-pressure portions including a housing having an inlet adapted to be connected to said high-pressure portions and an outlet adapted to be connected to said low-pressure portions, means forming within said housing a diaphragm chamber provided with diaphragm means adapted to be exposed to the pressure within said low-pressure portions, a main valve of large maximum flow capacity located between said inlet and said outlet in said housing, a fluid motor for operating and selecting the position of said main valve to control the flow from said inlet to said outlet, said housing having passage means extending from said inlet to said fluid motor, and a pilot valve operated by said diaphragm means located in series with said passage means for controlling the flow to said fluid motor to select the position of said main valve in accOrdance with the pressure of said low-pressure portions. 